But the time frame in question is 2015-2019, as the WGN TV deal will have expired after 2014 but their Comcast deal keeps them from having their own cable/satellite channel until 2020, at the earliest.

They would either need to move all games to CSN or sign another deal for OTA games, whether with WGN or another OTA station. I still think the side benefit of WGN America is too strong to throw that away.

I'm not sure why that free marketing of the ballpark matters all that much anymore. The big money is in the TV contracts.